1. Technical Field of the Invention
The present invention relates generally to mobile telecommunication networks. More particularly, and not by way of limitation, the invention is directed to a location-signaling system and method for large-scale end-to-end quality-of-service monitoring of packet-switched telecommunication networks.
2. Description of Related Art
The detailed analysis of live General Packet Radio System (GPRS) and UMTS networks is of increasing importance as traffic on these networks increases and traffic measurements become available. Traffic measurements from these networks are extremely useful when analyzing such areas as network utilization information, network performance information indicating whether the users are getting what they paid for or what they expect, bottleneck information identifying bottlenecks in the network, system enhancement information for enhancing the network so that identified problems are eliminated, and dimensioning information for re-dimensioning of cells, links, and the like.
In the case of a circuit-switched service such as voice, for example, it has conventionally been sufficient to measure the call intensities, call durations, and the ratio of blocked calls to successful calls. In the case of packet-switched services such as Web browsing, File Transfer Protocol (FTP) services, e-mail, Multimedia Messaging Services (MMS), and the like, the above tasks are not at all trivial because the end-to-end or user-perceived performance depends on the interaction of many protocols at different interfaces and on various protocol layers. Furthermore, the use of shared resources leads to rather complicated queuing phenomena, which are difficult to model and analyze.
It is envisioned that measurement-based network analysis will soon become a primary tool for the network operator. In order to perform the measurements in a cost-effective manner, the measurement equipment should be inexpensive, and the number of measurement points should be limited to reduce equipment costs and to minimize having to synchronize measurements taken at different points in the network.
Measurement-based characterization of GPRS networks has been described in a document entitled, “Wireless Service Usage and Traffic Characteristics in GPRS networks”, by Roger Kalden, Tamás Varga, Bianca Wouters, and Bart Sanders (18th International Teletraffic Congress, Berlin, Germany, 31 Aug. through 5 Sep. 2003). In this document, packets on the so-called Gi interface are captured. The Gi interface connects the Gateway GPRS Support Node (GGSN) with external packet data networks and service providers such as Internet Service Providers (ISPs). Based on the Gi traffic traces, detailed traffic and end-to-end performance analysis results are delivered to operators. In order to identify user sessions (i.e., which user the packets belong to), communications between the GGSN and a Remote Authentication Dial-In User Service (RADIUS) server are also monitored.
When it is also desired to relate the end-to-end quality measurements and traffic load measurements to cells, this can be accomplished by capturing cell-level location information. Concerning the availability of this location information, two types of networks can be differentiated. In the first network type, the cell-level location information is only available in the radio access network (network of base stations and their controllers), while in the second network type, the cell-level location information is also available in the core network (network connecting access networks and other service networks).
For example, the mobility management architectures of GPRS and UMTS are different. In order to track the mobile stations, the cells in a GPRS/UMTS service area are partitioned into several groups. To deliver services to a mobile station, the cells in the group covering the mobile station page the mobile station to establish a radio link. To detect a location change of a mobile station, the cells broadcast their cell identities. The mobile station periodically listens to the broadcast cell identity, and compares it with a cell identity stored in the mobile station's buffer. If the comparison indicates that the location has changed, then the mobile station sends a location update message to the network.
In the GPRS/UMTS (R′99), procedures such as Attach, Paging, and Location Update are defined separately for circuit-switched and packet-switched services. In the circuit-switched domain, cells are partitioned into location areas. Visiting Location Registers (VLRs) track the location area of the mobile station. In the packet-switched domain, the cells are partitioned into routing areas. A routing area is typically a subset of a location area. The SGSN tracks the routing area of the mobile station.
In GPRS, the SGSN also tracks the cell of a mobile station when packets are delivered between the mobile station and the SGSN. In UMTS, the cells in a routing area are further partitioned into UMTS Terrestrial Radio Access Network (UTRAN) routing areas (URA). The UTRAN tracks the URA and the cell of the mobile station.
In the evolution from GPRS to UMTS, the UTRAN radio access network has been introduced, and radio-related mobility management is moved from the core network to the UTRAN as described in “3GPP TS 23.060 V3.14.0, General Packet Radio Service, Service Description, Stage 2, Release 1999, 2002-12”. This means that cell-level and URA-level location information is not communicated towards the core network.
Cell-level location information can be captured from the Radio Resource Control (RRC) protocol at the so-called Iub interfaces between the base stations and the Radio Network Controller (RNC), or by extracting the information from the RNC. Both solutions, however, have disadvantages. Firstly, in the UTRAN, the number of Iub links can be rather high. Since reliable statistical analysis of a network requires a large amount of network-wide data, the first solution would be rather complicated. The number of measurement points would be rather high, and the problem of collecting and merging measurement data from these points to the data processing location would have to be solved. The second solution suffers from the disadvantage that users are identified in RRC cell-update signaling by temporary IDs (i.e., cell radio network temporary identity (RNTI) and UTRAN RNTI). The time-varying nature of these IDs makes it difficult to associate the transactions measured at higher aggregation points with a mobility pattern tracked in an RRC trace. Furthermore the needed information in the RNCs is stored in a vendor-specific manner. Therefore, a measurement system that can be used in any type of UTRAN cannot be based on extracting information from the RNC. Yet another drawback is that, in order to ensure network security, safe operation of network nodes, and the like, operators typically do not allow for measuring teams (which may be external) to access important network nodes such as the RNC. Therefore, a solution with passive tapping at a standardized network interface is favored.
Thus there is a particular need for a cost-effective passive monitoring method that can be applied in the current mobility management architecture of UMTS networks.